sour bread vs breadstuff

sour bread and breadstuff both are nouns.

Word	Noun	Adjective	Verb	Adverb
sour bread	Yes	No	No	No
breadstuff	Yes	No	No	No

As nouns, breadstuff is a hypernym of sour bread; that is, breadstuff is a word with a broader meaning than sour bread:

sour bread: made with a starter of a small amount of dough in which fermentation is active
breadstuff: food made from dough of flour or meal and usually raised with yeast or baking powder and then baked

Other hypernyms of sour bread include bread, staff of life.

sour bread (noun)	breadstuff (noun)
made with a starter of a small amount of dough in which fermentation is active	food made from dough of flour or meal and usually raised with yeast or baking powder and then baked
	flour or meal or grain used in baking bread